Estramustine (EM) has clinical utility in the treatment of prostate malignancies, although its pharmacological activity is independent of its constituent steroid/alkylating agent moieties. The objective of this proposal is to delineate the mechanism(s) by which EM induces cytotoxicity in normal, benign and malignant human prostate cells. By combining EM with dansyl chloride, a novel fluorescent probe (DNS-EM) is available to study drug uptake and intracellular distribution. Following chemical characterization and provide the biological activity of EM is not compromised by the dansylation, this compound may prove to have long term potential application in studies of EM's effects in animals and man. Using whole mount and thin section electron microscopy to investigate the effects of EM on microtubules, the cytomatrix and aspects of mitotic spindle organization, studies will focus on whether EM induces aberrations in the binding of microtubule associated proteins (MAP's) to microtubule components and to other cytoplasmic elements. The availability of specific monoclonal antibodies raised against MAP antigens will permit immunofluorescent microscopy studies of drug effects in short-term human prostate cultures and in an established human prostatic carcinoma cell line. EM may prove to be as useful to the study of MAP distribution and function as colchicine has been to the study of tubulin. In addition, it may represent a new class of antitumor drugs with anti-cytomatrix effects distinct from other chemotherapeutic agents.